The present invention relates to the field of high efficiency power amplifiers. More particularly, the invention relates to a circuitry for efficiently controlling the impedance at a connection point of a power supply to a power amplifier, being a feeding point, and providing enhancement of the voltage that is delivered to said power amplifier via an supplementary supply path that is used to connect the power supply to that point.
Several RF systems containing power amplifiers are characterized in recurrent periods of signals having large peak excursions, which should be handled, in order to improve the efficiency of these systems. One way to handle signals with large peak-to-average ratios is to control the DC power supply to a power amplifier. One voltage level is supplied to such a power amplifier whenever the instantaneous amplitude is below a given level (normal operating condition), and an enhanced (and higher) voltage level whenever the instantaneous amplitude is above said level. This solution is described for example, in WO 01/67598, which discloses circuitry for dynamically enhancing the operating voltage of an RF amplifier. However, efficiency of the voltage enhancement circuit disclosed therein may be further increased by controlling the impedance values at the connection point between the power amplifier and the power supply, during normal operation and during voltage enhancement time periods.
It is therefore desired to allow a power amplifier to work under different operating power supply voltages, in response to different input signals or conditions under which the power amplifier, or a component contained within it, operates. For example, in order to optimize the operation of a power amplifier, it would be beneficial to provide it with a DC power through a first supply path whenever the signal at its input is below a predetermined level, and add a second supplemental power supply path at instants wherein the signal at its input is above that level, thus enhancing the effective voltage supplied to said power amplifier. This type of solution allows operating a power amplifier in a relatively large dynamic range with high efficiency, as the enhanced operating voltage source is coupled to the circuit only when required by the large instantaneous amplitude.
It is an object of the present invention to provide circuitry that allows efficient enhancement of the voltage supplied to a power amplifier during required time periods.
It is another object of the present invention to provide circuitry for efficiently controlling the level of the voltage supplied to a power amplifier, via a supplementary supply path that is connected to the feeding point, during both the enhancement period, and periods of normal operation.
It is another object of the present invention to provide circuitry for efficiently controlling the impedance at that feeding point in the direction of the power amplifier and of the supplementary supply path, during both the enhancement period, and periods of normal operation.
Other objects and advantages of the invention will become apparent as the description proceeds.
The present invention is directed to a method for allowing efficient pulse-type enhancement of the voltage supplied to a power amplifier fed by a power supply being connected to the power amplifier at a first feeding point through a main supply path connected via a component, such as an inductor or a diode, having a high impedance to an enhancement pulse at the feeding point, and to a second feeding point. A supplementary supply path is provided, for enhancing the operating voltage to the power amplifier from the power supply, or from another power supply. A pair of a first and a second controllable impedances, such as a bipolar transistor or a FET, which are connected by a common contact are provided. Each controllable impedance is capable of being in a non-conducting state or in a variable level of conduction. One contact of the first controllable impedance is connected to the second feeding point, while the power supply, or another power supply, is connected across the contacts of the pair which are not connected at the common contact. A capacitor is connected between the common contact and the first feeding point. During the time period when no enhancement is required, simultaneously the first controllable impedance is caused to be in its conducting state and effectively connect the common contact to the second feeding point of the power supply, or another power supply, and the second controllable impedance is simultaneously caused to be in its non-conducting state and thereby, to effectively disconnect the common contact from the second feeding point and to allow the capacitor to charge to essentially the voltage of the power supply. During the time period when enhancement is required, the first controllable impedance effectively disconnects the common contact from one contact of the power supply, or another power supply, and the second controllable impedance is simultaneously controlled to be in a conduction level that corresponds to a desired enhancement voltage at the first feeding point, so as to increase the magnitude of the voltage at the common point, to which a contact of the capacitor is connected, and to cause an essentially similar increase in the voltage at the first feeding point, to which the other contact of the capacitor is connected.
Preferably, during the time period when enhancement is required, the first and/or the second controllable impedances are controlled by pulse signals having duration which is essentially similar to that time period.
The present invention is also directed to a circuitry for allowing efficient pulse-type enhancement of the voltage supplied to a power amplifier fed by a power supply being connected to the power amplifier at a first feeding point through a main supply path connected via a component having a high impedance to an enhancement pulse at the feeding point, such as an inductor or a diode, and to a second feeding point, that comprises:
a) a supplementary supply path for providing enhanced operating voltage to the power amplifier from the, or from another power supply;
b) a pair of a first and a second controllable impedances, such as a bipolar transistor or a FET, being connected by a common contact, each of which being capable of being in a non-conducting state or in a variable level of conduction, one contact of the first controllable impedance being connected to the second feeding point;
c) a power supply, being the, or another power supply, being connected across the contacts of the pair, which are not connected at the common contact, for providing enhanced operating voltage to the power amplifier;
d) a capacitor being connected between the common contact and the feeding point, for supplying at least a portion of the enhancement voltage through the feeding point during the time period;
e) circuitry for, simultaneously causing the first controllable impedance to be in its conducting state and effectively connect the common contact to the second feeding point of the, or another power supply, and the second controllable impedance to be in its non-conducting state, during the time period when no enhancement is required, and for causing the first controllable impedance to effectively disconnect the common contact from one contact of the, or another power supply and for simultaneously, controlling the second controllable impedance to be in a conduction level that corresponds to a desired enhancement voltage at the first feeding point, during the time period when enhancement is required.